Field of the Invention
This invention relates to driving a display apparatus, especially to a self-capacitive touch display panel and a method of driving a self-capacitive touch display panel.
Description of the Related Art
In general, an in-cell self-capacitive touch panel or a touch and display integrated self-capacitive touch panel can be applied to all kinds of portable electronic devices, such as a smart phone, a tablet PC and a notebook. Especially, the in-cell touch panel can achieve the thinnest touch panel design. The structures of the in-cell self-capacitive touch panel or the touch and display integrated self-capacitive touch panel are shown in FIG. 1. As shown in FIG. 1, the common electrodes VCOM of the self-capacitive touch panel 1 are all coupled to the touch and display integrated driving chip 10.
The conventional touch sensing methods of the in-cell self-capacitive touch panel are described as follows.
(1) The first conventional touch sensing method: Please refer to FIG. 2. As shown in FIG. 2, VCOM is the common electrode of the self-capacitive touch panel and SC is the display driving source of the self-capacitive touch panel. When the self-capacitive touch panel performs touch sensing, the touch sensing circuit of the self-capacitive touch panel will sense a touch sensing capacitance through the common electrode VCOM. Because the display driving source SC shown in FIG. 2 maintains at a fixed voltage level VF, the touch sensing capacitance sensed by the touch sensing circuit of the self-capacitive touch panel should be the total of the first capacitance C1 and the second capacitance C2. The current I generated by the common electrode VCOM will flow toward the first capacitance C1 and the second capacitance C2 respectively.
It should be noticed that since this touch sensing capacitance is very large, it will increase the touch sensing time of the self-capacitive touch panel, so that the display driving time of the self-capacitive touch panel will become shorter and the touch sensing performance will also become poorer.
(2) The second conventional touch sensing method: Please refer to FIG. 3. As shown in FIG. 3, the display driving source SC maintains high output impedance; therefore, the touch sensing capacitance sensed by the touch sensing circuit of the self-capacitive touch panel should be the total of the first capacitance C1 and the equivalent capacitance of the second capacitance C2 and the third capacitance C3 coupled in series. The current I generated by the common electrode VCOM will flow toward the first capacitance C1 and the second capacitance C2 respectively.
Although the touch sensing capacitance sensed by the second conventional touch sensing method is smaller than the touch sensing capacitance sensed by the first conventional touch sensing method, the touch sensing time of the self-capacitive touch panel is still too long, so that the display driving time of the self-capacitive touch panel is still too short and the touch sensing performance is still poor.